1. Field of the Invention
This invention relates in general to light curtain systems for detecting the intrusion of objects into a protected zone and, more particularly, to a light curtain system which utilizes a minimum of electrical components.
2. Description of the Related Art
Light curtain systems are employed in a variety of applications to sense the intrusion of objects in or around a prescribed area. Light curtains typically are employed for operator protection around machinery, such as punch presses, brakes, molding machines, automatic assembly equipment, robotic operations, and the like. Conventional light curtain systems employ infrared light beams which project a light beam across an area to be protected. Intrusion of the light beam by an object, such as an operator's hand, are sensed by the circuit and may then trigger a warning signal, shut the machinery down, or otherwise safeguard the area.
Conventional light curtain designs employ a light receiver circuit having a series of photo diodes which respond to light signals. Each photo diode typically is coupled with a single operational amplifier to provide a fast and sensitive detection; but which on the other hand is relatively complex, expensive and failure prone.
Accordingly, it is an object of the present invention to provide an improved light curtain that has a minimum of electrical components providing lower cost and more reliable operation.